> Can anyone explain (in simple terms) how the BSR works? I ve
> been trying to get my head round it all morning (while sorting out
> other disasters), and I m just plain confused

Have you got the manual ? (5MB)

http://www.microchip.com/download/lit/pline/picmicro/families/17c75x/30289b.
pdf

Section 7 explains memory in general and Section 7.8 explains
17C7xx BSR in particular. The notes with Table 7.5 have details
about selecting GPR or SFR. Although I'm not familiar with the
17C7xx, it seems to me that you have the currently active SFR
bank number in the lower nybble of BSR and the currently active
GPR bank number in the upper nybble (or that's how I read notes
1 and 2 anyway)

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